100 Blade Bulk Box. X-Acto's goal with the Z Series was to design, develop, and manufacture a No. 11 blade that is absolutely "best in class." They succeeded with significant improvement in sharpness, tip durability, and cutting performance, particularly in production and assembly line applications. A Zirconium Nitride coating on the cutting edge of Z Series blades adds significant strength to the blade, particularly the tip, for long life.